C27 Generator Set Engines Caterpillar

This application is equipped with an emergency shutdown switch. The switch is located on the control panel.

When the emergency stop switch is switched to the STOP position, the switch contacts are closed. When the emergency stop is activated, the switch supplies power to the control input of the ECM relay. As the relay is powered, the secondary contacts of the ECM relay are pulled open. As the contacts open, battery voltage is removed from the ECM. The switch contacts for the emergency stop are normally open in the RUN position. The secondary contacts for the ECM relay are normally closed.

The emergency stop switch also includes a circuit that allows the ECM to detect an emergency stop event. The contacts for this switch are normally closed in the RUN position. As the switch contacts open, digital return is removed from the ECM input.

Illustration 1	g02177270
Schematic for the emergency stop switch

Test Step 1. Inspect the Electrical Connectors and the Wiring

1. Turn the battery disconnect switch to the OFF position.
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   Illustration 2	g01207034
   Location of the ECM relay (typical left side engine view)

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   Illustration 3	g01210817
   Location of the engine interface connector (typical engine view)

2. Thoroughly inspect the connector for relay (1) and connector (2). Also, thoroughly inspect any other connectors that are associated with the circuit. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
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   Illustration 4	g01206959
   Terminal locations at the engine interface connector that are associated with the emergency stop switch (4) +Battery (23) Emergency stop

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   Illustration 5	g02177464
   Terminal locations at the connector for the emergency stop switch (5) +Battery (1) Emergency stop

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   Illustration 6	g01210818
   Terminal locations at the ECM relay that are associated with the emergency stop switch (2) −Battery (5) Emergency stop

3. Perform a 45 N (10 lb) pull test on each of the wires in the circuit for the emergency stop switch.

4. Check the torque of the allen head screw for the engine interface connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.

5. Check the harness and the wiring for abrasion and for pinch points from the battery to the ECM relay.

Expected Result:

All connectors, pins, and sockets are coupled and/or inserted, and the harness and wiring are free of corrosion, of abrasion, and of pinch points.

Results:

• OK - The connectors and wiring appear to be OK. Proceed to Test Step 2.

• Not OK - The connectors and/or wiring are not OK.

  Repair: Repair the wiring and/or the connectors. Replace parts, if necessary.

  STOP

Test Step 2. Check for Voltage at the Connector for the Emergency Stop Switch

1. Disconnect the connectors for the emergency stop switch.

2. Turn the battery disconnect switch to the ON position.

3. Measure the voltage between terminal 5 on the harness side of the connector for the emergency stop switch and the engine ground stud.

Expected Result:

The correct voltage is 24 ± 3 VDC.

Results:

• OK - The voltage is 24 ± 3 VDC. The supply voltage is reaching the connector for the emergency stop switch. There may be a problem with the emergency stop switch. Proceed to Test Step 4.

• Not OK - The voltage is not 24 ± 3 VDC. The supply voltage is not reaching the connector for the emergency stop switch. There is a problem in the circuit between the emergency stop switch and the battery. Proceed to Test Step 3.

Test Step 3. Check the Emergency Stop Switch

1. Disconnect the engine interface connectors.

2. Measure the voltage between terminal 4 on the engine harness side of the engine interface connectors and the engine ground stud.

Expected Result:

The correct voltage is 24 ± 3 VDC.

Results:

• OK - The voltage is 24 ± 3 VDC.

  Repair: There is supply voltage at the engine interface connectors, but not at the connector for the emergency stop switch.

  There is a problem in the harness between the engine interface connectors and the connector for the emergency stop switch. The problem may be in a connector. Repair the harness and/or the connector. Replace parts, if necessary. Refer to Troubleshooting, "Inspecting Electrical Connectors".

  STOP

• Not OK - The voltage is not 24 ± 3 VDC.

  Repair: Supply voltage is not reaching the engine interface connector. There is a problem in the circuit from the battery to the engine interface connector. Ensure that the circuit breaker for the emergency stop switch is not tripped. Repair the harness and/or the connector. Replace parts, if necessary.

  Refer to Troubleshooting, "Inspecting Electrical Connectors".

  STOP

Test Step 4. Check the Emergency Stop Switch

1. Ensure that the emergency stop switch is in the RUN position.

2. Measure the resistance between terminals 1 and 5 on the switch side of the connector for the emergency stop switch.

   An open circuit condition is the correct measurement with the emergency stop switch in the RUN position.

3. Place the emergency stop switch in the STOP position.

4. Again, measure the resistance between terminals 1 and 5 on the switch side of the connector for the emergency stop switch.

   A short circuit condition is the correct measurement with the emergency stop switch in the STOP position.

Expected Result:

The measurements agree with the results that are stated above.

Results:

• OK - The measurements agree with the results that are stated above. The emergency stop switch is operating correctly. There may be a problem in the harness between the emergency stop switch and the engine interface connector. Reconnect the connectors for the emergency stop switch. Proceed to Test Step 5.

• Not OK - The measurements did not agree with the results that are stated above.

  Repair: There is a problem with the emergency stop switch. Replace the switch. Restore all wiring to the original configuration. Verify that the repair resolves the original problem.

  STOP

Test Step 5. Check the Harness Between the Connector for the Emergency Stop Switch and the Engine Interface Connector

1. Ensure that the emergency stop switch is in the RUN position.

2. Measure the resistance between terminals 4 and 23 on the switch side of the engine interface connector.

   An open circuit condition is the correct measurement with the emergency stop switch in the RUN position.

3. Place the emergency stop switch in the STOP position.

4. Again, measure the resistance between terminals 4 and 23 on the switch side of the engine interface connector.

   A short circuit condition is the correct measurement with the emergency stop switch in the STOP position.

Expected Result:

The measurements agree with the results that are stated above.

Results:

• OK - The measurements agree with the results that are stated above. The harness between the emergency stop switch and the engine interface connector is OK. There may be a problem in the harness between the engine interface connector and the ECM relay. Connect the connectors for the engine interface connector. Proceed to Test Step 6.

• Not OK - The measurements did not agree with the results that are stated above.

  Repair: There is a problem in the circuit between the engine interface connector and the emergency stop switch. Repair the harness and/or the connectors. Replace parts, if necessary. Verify that the repair resolves the original problem.

  STOP

Test Step 6. Check the Operation of the Emergency Stop Switch

1. Ensure that the battery disconnect switch is in the OFF position.

2. Disconnect the connector from the ECM relay.

3. Place the emergency stop switch in the RUN position.

4. Turn the battery disconnect switch to the ON position.

5. Measure the voltage between terminal 5 of the connector for the ECM relay and the engine ground stud.

   The correct voltage is 0 V.

6. Place the emergency stop switch in the STOP position.

7. Again, measure the voltage between terminal 5 of the connector for the ECM relay and the engine ground stud.

   The correct voltage is 24 ± 3 VDC.

8. Turn the battery disconnect switch to the OFF position.

Expected Result:

The voltage at the ECM relay is 0 V with the emergency stop switch in the RUN position. The voltage at the ECM relay is 24 ± 3 VDC with the emergency stop switch in the STOP position.

Results:

• OK - The voltages are correct for the conditions that are stated above. The correct control voltage is reaching the ECM relay. The circuit for the emergency stop switch is operating correctly at this time. There may be a problem with the ECM relay. Proceed to Test Step 7.

• Not OK - The voltages are correct for the conditions that are stated above.

  Repair: The circuit is OK at the engine interface connector, but the ECM relay is not receiving the correct voltage. There is a problem in the circuit between the engine interface connector and the connector for the ECM relay. Repair the harness and/or the connectors. Replace parts, if necessary.

  STOP

Test Step 7. Check for Battery Voltage on the Secondary Circuit of the ECM Relay

1. Place the battery disconnect switch in the ON position.

2. Ensure that the emergency stop switch is in the RUN position.

3. Ensure that the connector for the ECM relay is connected.

4. Carefully insert a 7x-1708 Multimeter Probe into terminal 3 at the connector

5. Measure the voltage between terminal 3 of the connector for the ECM relay and the engine ground stud.

Expected Result:

24 ± 3 VDC is available at terminal 3 of the connector at the ECM relay.

Results:

• OK - 24 ± 3 VDC is available at terminal 3.

  Repair: Power is available at the output of the secondary circuit at the ECM relay. There may be a problem in the harness between the ECM relay and the ECM. Perform the following procedure:

  1. Use the 7x-1708 Multimeter Probe to check for battery voltage between the engine ground stud and the following connector terminals at the ECM:

     • P1-48

     • P1-52

     • P1-53

     • P1-55

     • P1-57
  If battery voltage is present at the ECM, there may be a problem with the ECM. Before you consider replacing the ECM, consult with the Dealer Solutions Network (DSN).

  If battery voltage is not available at the ECM, there is a problem in the harness between the ECM relay and the ECM. Repair the harness or replace the harness.

  Verify that the repair eliminates the original problem.

  STOP

• Not OK - 24 ± 3 VDC is not available at terminal 3 of the connector at the ECM relay.

  Repair: Check that the ECM breaker is not tripped. If the breaker is OK, there is a problem in the circuit between the battery and the ECM relay. The problem may be in a connector. Repair the harness and/or connector.

  Verify that the repair eliminates the original problem.

  STOP